The retractable landing gears of airplanes are conventionally retractable into a volume that can be closed in flight by one or more flaps that form a door. It is known to actuate the flaps, in order to open or close them, with the aid of actuating means such as hydraulic cylinders. One cylinder per flap can be provided.
However, in order to open two flaps, in particular two constituent flaps of a two-flap door, as the number of certain parts involved is doubled; i.e. two cylinders are necessary, as well as two associated opening and closing mechanisms. This results in an increased mechanical complexity and higher mass. Furthermore, since each cylinder is typically linked to the structure of the aircraft on each side of the structure, more or less directly below the tipping axis of each of the flaps, the lever arm between the application point of a force by the cylinder and the rotation axis of the flap is short. This requires the use of cylinders that are and are thus heavy, creating significant forces on the structure of the aircraft.
Two-flap doors that are actuated by a single cylinder are also known. This is commonly the case for landing gear doors that are located at the nose of the airplane. In known devices comprising a single cylinder for actuating the door, two tie rods are linked to the flaps and are connected together at a pivot point. This pivot point is generally located at the end of a transverse arm. The other end of the transverse arm is connected to the structure of the aircraft. The raising or lowering of the pivot point, under the effect of a cylinder linked to the transverse arm on one side and to the structure of the aircraft on the other side, causes the flaps of the door to open or close. In the known devices, two zones are created for introducing forces into the structure of the aircraft, firstly in the region of a link between the cylinder and the structure, and secondly at the link, typically a pivot link, between the transverse arm and the structure. The introduction of transverse forces into an aircraft is not desirable, in particular if these are not absorbed directly by a central beam of the aircraft.
The known devices are bulky, have complex dynamics, and/or bring about absorption of forces at least at two points on the structure of the aircraft, which have to be reinforced.
The aim of the present embodiments described herein is to provide a device for opening or closing two flaps of a landing gear door of an aircraft, which is optimized with regard to its makeup and the forces transmitted to the structure of the aircraft.
To this end, provision is made, according to a first aspect of an embodiment, of a device for the concomitant opening or closing of two flaps of a door of an aircraft retractable landing gear, the two flaps pivoting about two approximately parallel longitudinal pivot axes that define a closing plane of the flaps. The device comprises a single actuating means that is able to open and close the flaps by modification of its length, the actuating means comprising a fixed end linked at a force-absorbing point to the structure of the aircraft, the actuating means furthermore comprising a movable part. The device further comprises a swinging arm having a first end linked by a first link to the structure, and a second end linked by a second link to the movable part of the actuating means, the first link being a pivot and the second link having a degree of freedom about an axis parallel to the axis of the pivot, the device being configured such that the second end of the swinging arm moves away from or toward the closing plane PF of the flaps during the extension or the retraction of the actuating means. The second end of the swinging arm is respectively linked to a first tie rod linked to a first of the two flaps, and to a second tie rod linked to a second of the two flaps.
Such a device has simple dynamics and can be compact and lightweight. It also makes it possible to transfer all or almost all of the mechanical forces generated during the opening or closing of a landing gear door to a single point for absorption of forces by the structure of the aircraft in question, namely the linking point between the fixed end of the actuating means and the structure to which it is linked.